Multicast over DMVPN,IPSEC,GRE

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Ok im labbing this up at the moment in preparation for a new project, the basic layout is:

Firstly when I just setup a routed connection between router 1&2 everything worked fine:

Switch1 - Vlan1: ip igmp snooping

Router1 - internal interface: ip pim sparse-dense-mode

Router1 - external interface: ip pim sparse-dense-mode

Router2 - external interface: ip pim sparse-dense-mode

Router2 - internal interface: ip pim sparse-dense-mode

Switch2 - Vlan1: ip igmp snooping

Using PRTG I see that the bitrate all the way through is consistently ~150kb/s (my video streaming bitrate)

Then I tested with a DMVPN configured between Router 1&2 once again everything worked fine.

The only changes were, I removed ip pim sparse-dense-mode from the external router interfaces and put it on the tunnel interfaces.

When I use PRTG to observe the traffic, it was ~150kb/s all the way up to Router1 internal interface, then both of the DMVPN interfaces and Router2 internal interface showed ~300kb/s. The switch ports for client 1 & 2 only showed ~150kb/s.

So... what am I missing here? Why is the bandwidth double across the GRE IPSEC connection?

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This is interesting. Can you please post the entire configuration from both your routers? Also, if you have the option of increasing or decreasing the multicast data stream rate, is the amount of data carried by the DMVPN always roughly twice the rate of the original stream?

I believe this is because the DMVPN host has to encrypt each packet as if it is an individual stream due to the way IPSec is processed for each destination. I do not think the DMVPN host can encrypt/encapsulate a single packet then sent it to 2 different destinations. Correct me if I am wrong but I believe IPSec encrypted packet's original source and destinations ip headers are encapsulated with the rest of the data and a new source and destination header is applied and these new source and destination headers are for the individual destination routers ip instead of just being a multicast destination ip.